We are doing science for policy
The Joint Research Centre (JRC) is the European Commission's science and knowledge service which employs scientists to carry out research in order to provide independent scientific advice and support to EU policy.
A new JRC assessment of the future water resources of the Danube River Basin finds that climate change beyond 2°C would lead to increased flooding and water scarcity, significantly drier summer months and substantial flood damage in cities along the Danube River and its tributaries.
The JRC report gives an integrated analysis of the integrated effects of changes in climate, land use, and water consumption on the Danube River Basin. Based on research by the JRC Danube WEFE (Water-Energy-Food-Ecosystems) project, the study was prepared to support the revision of the International Commission for the Protection of the Danube River (ICDPR) Strategy on Adaptation to Climate Change.
Using the JRC’s LISFLOOD water resources model, Euro-Cordex climate scenarios (bias-adjusted by the JRC), LUISA (Land Use-based Integrated Sustainability Assessment) land use projections, and water demand and consumption projections, two 30-year climate windows were compared to the 1981-2010 control climate window.
The Danube River Basin
The Danube River Basin is the world's most international river basin as it includes the territories of 19 countries, 11 of which are in the EU. It is home to 83 million people and hundreds of fish species. The Danube River is a major transportation route with links to the Rhine River, enabling transport from the Back Sea to the North Sea. The river delta is an important habitat for wildlife and fisheries and has been designated a Ramsar wetlands site and a UNESCO world heritage site.
Findings of the report
The authors conclude climate change is the dominant factor driving the change in water resources in the Danube River Basin. Land-use change (urban expansion) also plays a role, as does greater future demand for water due to GDP growth etc., which reduces the overall water availability.The Pasterze Glacier (AT, Grossglockner), which flows into the Danube basin, is drastically receding due to rising temperatures.
Meeting the objectives of the Paris Climate Agreement of 2015 will lead to substantially less severe impacts for the water resources of the Danube River Basin compared to the impacts of climate change beyond 2°C degrees global temperature increase. Issues with flooding and (especially) summer water scarcity, which are already problems under current climate conditions, are projected to increase.
The summer months are projected to be 15% drier than during the period 1981-2010, and up to 20% drier in the southern Danube River Basin area. Projections for the end of the century (2070-2099) under a more extreme climate change scenario (RCP 8.5, with high greenhouse gas emissions leading to a temperature increase of around 3.5 to 4°C) show a more extreme impact on water resources, with drier conditions in the southern part of the Danube due to a reduction in precipitation of more than 30% during the summer months (June-August). For the upper and middle parts of the main Danube River, peak river flows are projected to be 10-30% greater than peak flows under current climate conditions.
Projections for the Danube River Basin under a 2°C climate change scenario are for generally wetter conditions and higher flooding risks, but drier summer months, especially in the southern regions. For the main Danube River, peak river flows are projected to be 10-20% greater than under current climate conditions. Given the projected urban expansion of some of the region's capital cities (Vienna, Budapest, Belgrade) which are situated along the Danube River or its main tributaries (Zagreb), the risk of flood damages will increase significantly.
Water scarcity is projected to be more severe and persistent, especially during the summer months in the southern and eastern Danube basin. Under a temperature increase of 2°C, water exploitation will increase in some seasons in Bulgaria, Hungary, Serbia, Bosnia-Herzegovina and Romania, but will decrease in other seasons and areas. The end-of-the-century RCP 8.5 climate scenario shows substantial increases in water scarcity in Bulgaria, Serbia, Romania, Hungary, Slovakia and Moldova, especially during the summer months.
Impact on economic activities
A number of sectors requiring water – such as arable and irrigated agriculture and the local energy sector – will likely suffer longer periods of a substantial lack of water, which may lead to loss of production.
Periods of low river flows are projected to be an issue of increasing concern in the southern tributary rivers to the Danube, leading to transport difficulties, reduced water availability for cooling thermal power plants, drinking water, hydropower reservoir water supply, and ecological issues.
The regions most likely to be affected by water scarcity may actually stay the same, but the water scarcity problem they experience is projected to intensify. However, the population affected by water scarcity will be either stable or even decrease, as population figures are projected to drop in several Danube countries, such as Bulgaria, Serbia and Romania.
Groundwater recharge is projected to increase during winter months, and to decrease during the summer.
Urbanised areas are projected to become increasingly vulnerable to urban flooding problems.